The thinker: Inside the mind of prized intellectual Amartya Sen

An intellectual who picks up honorary degrees in his spare time, Amartya Sen believes in reason and human rights. Just don't call him idealistic, says Sholto Byrnes

The Idea of Justice is billed as Amartya Sen's most ambitious book yet. This is quite a claim for a man whose publications on famine are acknowledged as having changed global perceptions on poverty and food production, and whose work on welfare economics significantly contributed to the United Nations' Human Development Index. He has been garlanded with honours, including the Nobel Prize for Economics in 1998. So celebrated is he as a thinker and academic that, asked what Sen does at weekends, his publisher replied, "he collects honorary degrees".

And not just at weekends, it turns out: when we meet on a Wednesday at Trinity College, Cambridge, where Sen was master from 1998-2004 (the first Asian person to be head of an Oxbridge college), he reveals: "I'm off to Dublin tomorrow, to receive an honorary degree." When Trinity College, Dublin rang to offer him the scroll, he had to explain that he'd just received one from University College, Dublin. A delay in conferring the degree was agreed upon because, as Sen joked, he wasn't used to going to Dublin that often.

After a lunch enlivened by the kind of high- table gossip Anthony Powell would have relished, we repair to his office and I ask him about his "most ambitious" book. "Well, those are my publisher's words," he begins, "although that doesn't mean I disagree. I am, of course, mainly trained as an economist, although I have been writing on philosophy for more than 40 years now. I'm trying to make sense of thinking about justice in a way that's philosophically engaged, but which will also have a reach to the public. It's taking all the very difficult subjects but trying to make them accessible."

He changes tack, musing about the word "ambition" in a way that speaks more to the philosopher than the economist in him. (He is a professor in both disciplines.) "I don't know that ambitiousness is a virtue in a book," he elaborates. "Correctness is. Relevance is, and reach is. My own ambitiousness may be quite important to me, but may not be for the reader." He pauses, chuckling at his audience's imaginary response. "What the hell do I care what this man's ambition is?"

Sen is 75 but his mind has a sharpness that those decades his junior would envy. He does, however, display some old-fashioned donnish unworldliness when it comes to technology. In his car, first the rear and then the front windscreen-wipers spring to life to his surprise and bafflement, and it is some time before he can discover the means of turning them off, while a technician who comes to fix the phone in his office discovers that the reason it is not working is... the power lead is not plugged in. Both of these instances he greets with a humour and lack of irritation consistent with his exquisite manners and infectious cheerfulness.

His book's starting point is that identifying redressable injustice, rather than positing what would be the perfectly just society, is central to the theory of justice itself. How do our intuitive, subjective ideas relate to this, I ask. "It relates well to it. I believe that our first presumptions about justice are not overtly reason-based. We have a sense of injustice much more than we have a sense of justice." He cites 18th-century concerns about slavery and the subjugation of women, and Marx's focus on the dispossessed.

"But after that, we ask why it is unjust. So our thinking about justice takes the form of defending or demolishing our own or others' intuitions, and these are matters of reasoning." He concedes that he has been criticised for underestimating the power of unreason, that simple conviction many have in the rightness of their moral positions which may, from another view, be mere prejudice or localised, inherited tradition. (He famously took issue with Singapore's Lee Kuan Yew over the "Asian Values" argument that liberal democratic ideas were culturally specific to the West.) "But when people say that non-whites are inferior, or that women don't have the skills that men do, or there's a reason why some people are lower caste, born into less able families: for this they have reasons, terrible reasons, and as such they're examinable, discussable, scrutinisable and – thank God – dismissable. My claim is that the moment you begin a dispute you have no option but to engage in reasoning."

Is he then, I ask, an idealist about the power of reason to defeat unreason? "There are some words I try not to use," he replies, "and idealist is one of them. That could mean someone who was hopelessly unrealistic or someone who was so enamoured of his ideas that he would not examine the opposite argument. Do I believe that reason will vanquish unreason? Not always, but it's very important to ask what would reason demand."

Sen's belief is that ideas of justice based on reasoning are universal, and are not just drawn primarily from the Western tradition of liberal democracy. In his book he refers to two Sanskrit words for justice: niti – "organisational propriety and behavioural correctness" and nyaya – "a comprehensive concept of realised justice". It is this latter concept, he says, on which we should focus. And this pragmatic view runs deep within him.

Born in 1933 in the grounds of Santiniketan, the college established by the Bengali poet and fellow Nobel Laureate Rabindranath Tagore, Sen once said: "I seem to have lived all my life in one campus or another." After studying at Calcutta and Trinity College, Cambridge, he was offered his first chair (in economics) at the newly created Jadavpur University in India, aged 22. Returning to Trinity as a prize fellow, he broadened his studies to include philosophy, and has since held positions at Oxford, Harvard, the LSE and Delhi.

But a career in academia hasn't diminished his engagement with the outside world. The influence of Tagore's school, with its emphasis on intellectual curiosity and the wider world, has never left him. "Any kind of interest in examination performance and grades was severely discouraged," he has recalled.

This emphasis on what is practical seems sensible, admirable even, given the usual academic preference for tight arguments and conclusions. But it won't answer the criticism of those who take issue with his definitions of two concepts crucial to his theory of justice: democracy, which in his view is reliant on the presupposition of open societies; and human rights, which he is content to describe as "ethical assertions" rather than hard moral facts.

Isn't there a lot of "loose talk", as he puts it in his book, about democracy and human rights? "There's loose talk everywhere," he readily agrees, immediately adding the caveat that, "If you were to shun loose talk, you'd have very little conversation in the world. But I don't think that just because many statements are not well-defined, that means we should reject them. I think you'd be left with very dry, boring talk, very little use for poetry, and you wouldn't be allowing people the liberty for imaginative discussions, which I think is a huge part of humanity." And, he could have added, for his idea of justice.

My view, as I leave Professor Sen (he urges me to call him to continue our conversation) is that, however much he dislikes the word, he is an idealist: an idealist for democracy, justice and universal human rights that he believes will win through the power of reason. As it happens, I don't agree – but I depart feeling challenged, invigorated and questioning after my encounter with one of the most remarkable thinkers alive today. He is kind enough to imply, amid our disagreement, that that is a good enough start for him.

The extract

The Idea of Justice, By Amartya Sen (Penguin £25)

'... At the heart of the particular problem of a unique impartial resolution of the perfectly just society is the possible sustainability of plural and competing reasons for justice... Let me illustrate the problem with an example in which you have to decide which of three children – Anne, Bob and Carla – should get a flute about which they are quarrelling...'